More evidence suggests Earth is entering a sixth extinction-level event

This site may earn affiliate commissions from the links on this page. Terms of use.

A new paper from Stanford, Princeton, and Berkeley suggests that the world has begun a sixth extinction-level event, this one driven primarily by humankind. This new research indicates that the fossil record clearly shows that species of every sort are becoming extinct far more rapidly than the historical background rate would suggest, and that much of the change is driven by humanity, including the impact of climate change.

The previous extinction events. Percentage to the left is total number of species’ killed. Image courtesy of Wikipedia

The report set out to answer whether current extinction rates for mammals and vertebrates were higher than the highest background level observable through the fossil record, how extinction rates have changed over time within observed history, and how many years it would take species to go extinct if the background extinction rate had held steady. The so-called “background rate” of extinction is extremely important. It’s the number of species that we can predict would have gone extinct, even without outside intervention.

While the point of the paper was to measure the impact of humans, thousands of species of plants, animals, reptiles, amphibians, and birds have historically gone extinct without any human intervention whatsoever, while others (the dodo bird, Steller’s sea cow, the passenger pigeon, and the Rodriguez giant tortoise) were killed off by humans long before climate change was a concern. A high background extinction rate will make any modern departure from the norm less serious-looking, while a low background extinction rate emphasizes the modern departure from historical norms.

In the past, scientists have estimated that species tend to go extinct at a rate between 0.1 and 1 species per million species per year, but for the purposes of this paper, the team of researchers decided on a background extinction rate of 2E/MSY (meaning two species for every million species, every million years). Because we can’t be certain of accounting for every single species, including species that do not decay and leave fossilized materials, there’s always going to be some slippage in the figures — but we can still chart the extinction rate of well-represented species and compare against historical records when that data is available.

This chart shows the number of extinct creatures since 1500 and 1900 for each available species classification. The Highly Conservative rates include only species no longer believed to exist at all, anywhere on Earth. While it’s true that some of these species are later rediscovered, the rate of rediscovery is extremely low and typically confined to tiny, endangered populations located in an heretofore-unknown spot. The Conservative table includes those species believed to be extinct in the wild or possibly extinct. In both cases, the extinction rates shot up after 1900, once the industrial revolution and modern record keeping where both underway.

These charts show the observed extinction rates for various species measured against the background extinction rate for both the “Highly Conservative” and “Conservative” estimates. Even assuming a much higher background extinction rate of 2E/MSY, the die-off rate for all species has been orders of magnitude above background. Statistically, the die-off in amphibians would have taken an estimated 11,600 years to occur naturally, while even the reptile species die-off rate would have taken 800 years — not the 114 years that have passed since 1900.

Why should humans care?

Sweeping species loss under the rug or dismissing it as ecological scareism is a serious mistake. The loss of a single species may seem of minor importance — after all, does the world actually need tree frogs? In theory, no, it doesn’t — but while the loss of any single species is a minor event in the grand scheme of things, the loss of hundreds can create substantial hardship for humanity. The loss of honeybee colonies in the US could drive food prices up, while the collapse of multiple off-shore fisheries has already created real problems for the communities that relied upon them.

It’s impossible to estimate the cost of species extinction, in part because we literally don’t know what we might lose. Horseshoe crabs are an example of a species under pressure as a result of human activity that’s also extremely useful to human medicine. Unlike other species, which rely on hemoglobin in the blood for oxygen transport, horseshoe crabs use hemocyanin. Horseshoe crab blood is used to manufacture Limulus amebocyte lysate (LAL), which reacts with bacterial endotoxins. It’s an essential compound used to ensure that medical devices and medications themselves aren’t infected with bacteria before being given to people. LAL can even detect some fungal infections far faster than other forms of testing.

If horseshoe crabs had gone extinct before we discovered these properties, we’d likely have never known they existed in the first place. While I’ve picked relatively simple example, as more species go extinct, it destabilizes the entire ecological web around them. In some cases, other species that might have preferred the first as a food source will adapt. In other cases, they can’t.

We don’t know what we don’t know — which means we don’t know at what point life on Earth reaches a tipping point and begins to drastically change. One thing we do know about past extinction events, regardless of their causes, is that they were marked by the emergence of very different environmental conditions and species. The most famous extinction event, the K-T impact that destroyed the non-avian dinosaurs, cleared the way for mammals to evolve and ascend. Life, as a whole, is extremely resilient, but no single species is guaranteed survival — including ours.

Tagged In

This site may earn affiliate commissions from the links on this page. Terms of use.

ExtremeTech Newsletter

Subscribe Today to get the latest ExtremeTech news delivered right to your inbox.

Email

This newsletter may contain advertising, deals, or affiliate links. Subscribing to a newsletter indicates your consent to our
Terms of Use and
Privacy Policy. You may unsubscribe from the newsletter at any time.